In some navigation and robotic applications, high resolution measurements of linear and angular displacement of a moving object are critical to the success of the applications. Optical or mechanical encoders have been commonly used in these types of applications to measure the linear or angular displacement of an object relative to another surface. However, these encoders either require special precision markings on the surface for the optical sensor or physical contact with the surface for the mechanical sensor to measure the relative changes accurately.
Because of these physical requirements, optical and mechanical encoders are often too difficult if not impossible to implement in many applications. Accordingly, there is a need for an alternative and inexpensive approach to take the place of these encoders so that the foregoing physical requirements can be eliminated.